Vendor in containers/buildah v1.14.3

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

8 files changed, 922 insertions, 0 deletions

diff --git a/vendor/github.com/containerd/containerd/log/context.go b/vendor/github.com/containerd/containerd/log/context.go
new file mode 100644
index 000000000..31f1a3ac0
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/log/context.go
@@ -0,0 +1,90 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package log
+
+import (
+	"context"
+	"sync/atomic"
+
+	"github.com/sirupsen/logrus"
+)
+
+var (
+	// G is an alias for GetLogger.
+	//
+	// We may want to define this locally to a package to get package tagged log
+	// messages.
+	G = GetLogger
+
+	// L is an alias for the standard logger.
+	L = logrus.NewEntry(logrus.StandardLogger())
+)
+
+type (
+	loggerKey struct{}
+)
+
+// TraceLevel is the log level for tracing. Trace level is lower than debug level,
+// and is usually used to trace detailed behavior of the program.
+const TraceLevel = logrus.Level(uint32(logrus.DebugLevel + 1))
+
+// RFC3339NanoFixed is time.RFC3339Nano with nanoseconds padded using zeros to
+// ensure the formatted time is always the same number of characters.
+const RFC3339NanoFixed = "2006-01-02T15:04:05.000000000Z07:00"
+
+// ParseLevel takes a string level and returns the Logrus log level constant.
+// It supports trace level.
+func ParseLevel(lvl string) (logrus.Level, error) {
+	if lvl == "trace" {
+		return TraceLevel, nil
+	}
+	return logrus.ParseLevel(lvl)
+}
+
+// WithLogger returns a new context with the provided logger. Use in
+// combination with logger.WithField(s) for great effect.
+func WithLogger(ctx context.Context, logger *logrus.Entry) context.Context {
+	return context.WithValue(ctx, loggerKey{}, logger)
+}
+
+// GetLogger retrieves the current logger from the context. If no logger is
+// available, the default logger is returned.
+func GetLogger(ctx context.Context) *logrus.Entry {
+	logger := ctx.Value(loggerKey{})
+
+	if logger == nil {
+		return L
+	}
+
+	return logger.(*logrus.Entry)
+}
+
+// Trace logs a message at level Trace with the log entry passed-in.
+func Trace(e *logrus.Entry, args ...interface{}) {
+	level := logrus.Level(atomic.LoadUint32((*uint32)(&e.Logger.Level)))
+	if level >= TraceLevel {
+		e.Debug(args...)
+	}
+}
+
+// Tracef logs a message at level Trace with the log entry passed-in.
+func Tracef(e *logrus.Entry, format string, args ...interface{}) {
+	level := logrus.Level(atomic.LoadUint32((*uint32)(&e.Logger.Level)))
+	if level >= TraceLevel {
+		e.Debugf(format, args...)
+	}
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/compare.go b/vendor/github.com/containerd/containerd/platforms/compare.go
new file mode 100644
index 000000000..3ad22a10d
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/compare.go
@@ -0,0 +1,229 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import specs "github.com/opencontainers/image-spec/specs-go/v1"
+
+// MatchComparer is able to match and compare platforms to
+// filter and sort platforms.
+type MatchComparer interface {
+	Matcher
+
+	Less(specs.Platform, specs.Platform) bool
+}
+
+// Only returns a match comparer for a single platform
+// using default resolution logic for the platform.
+//
+// For ARMv8, will also match ARMv7, ARMv6 and ARMv5 (for 32bit runtimes)
+// For ARMv7, will also match ARMv6 and ARMv5
+// For ARMv6, will also match ARMv5
+func Only(platform specs.Platform) MatchComparer {
+	platform = Normalize(platform)
+	if platform.Architecture == "arm" {
+		if platform.Variant == "v8" {
+			return orderedPlatformComparer{
+				matchers: []Matcher{
+					&matcher{
+						Platform: platform,
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v7",
+						},
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v6",
+						},
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v5",
+						},
+					},
+				},
+			}
+		}
+		if platform.Variant == "v7" {
+			return orderedPlatformComparer{
+				matchers: []Matcher{
+					&matcher{
+						Platform: platform,
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v6",
+						},
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v5",
+						},
+					},
+				},
+			}
+		}
+		if platform.Variant == "v6" {
+			return orderedPlatformComparer{
+				matchers: []Matcher{
+					&matcher{
+						Platform: platform,
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v5",
+						},
+					},
+				},
+			}
+		}
+	}
+
+	return singlePlatformComparer{
+		Matcher: &matcher{
+			Platform: platform,
+		},
+	}
+}
+
+// Ordered returns a platform MatchComparer which matches any of the platforms
+// but orders them in order they are provided.
+func Ordered(platforms ...specs.Platform) MatchComparer {
+	matchers := make([]Matcher, len(platforms))
+	for i := range platforms {
+		matchers[i] = NewMatcher(platforms[i])
+	}
+	return orderedPlatformComparer{
+		matchers: matchers,
+	}
+}
+
+// Any returns a platform MatchComparer which matches any of the platforms
+// with no preference for ordering.
+func Any(platforms ...specs.Platform) MatchComparer {
+	matchers := make([]Matcher, len(platforms))
+	for i := range platforms {
+		matchers[i] = NewMatcher(platforms[i])
+	}
+	return anyPlatformComparer{
+		matchers: matchers,
+	}
+}
+
+// All is a platform MatchComparer which matches all platforms
+// with preference for ordering.
+var All MatchComparer = allPlatformComparer{}
+
+type singlePlatformComparer struct {
+	Matcher
+}
+
+func (c singlePlatformComparer) Less(p1, p2 specs.Platform) bool {
+	return c.Match(p1) && !c.Match(p2)
+}
+
+type orderedPlatformComparer struct {
+	matchers []Matcher
+}
+
+func (c orderedPlatformComparer) Match(platform specs.Platform) bool {
+	for _, m := range c.matchers {
+		if m.Match(platform) {
+			return true
+		}
+	}
+	return false
+}
+
+func (c orderedPlatformComparer) Less(p1 specs.Platform, p2 specs.Platform) bool {
+	for _, m := range c.matchers {
+		p1m := m.Match(p1)
+		p2m := m.Match(p2)
+		if p1m && !p2m {
+			return true
+		}
+		if p1m || p2m {
+			return false
+		}
+	}
+	return false
+}
+
+type anyPlatformComparer struct {
+	matchers []Matcher
+}
+
+func (c anyPlatformComparer) Match(platform specs.Platform) bool {
+	for _, m := range c.matchers {
+		if m.Match(platform) {
+			return true
+		}
+	}
+	return false
+}
+
+func (c anyPlatformComparer) Less(p1, p2 specs.Platform) bool {
+	var p1m, p2m bool
+	for _, m := range c.matchers {
+		if !p1m && m.Match(p1) {
+			p1m = true
+		}
+		if !p2m && m.Match(p2) {
+			p2m = true
+		}
+		if p1m && p2m {
+			return false
+		}
+	}
+	// If one matches, and the other does, sort match first
+	return p1m && !p2m
+}
+
+type allPlatformComparer struct{}
+
+func (allPlatformComparer) Match(specs.Platform) bool {
+	return true
+}
+
+func (allPlatformComparer) Less(specs.Platform, specs.Platform) bool {
+	return false
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/cpuinfo.go b/vendor/github.com/containerd/containerd/platforms/cpuinfo.go
new file mode 100644
index 000000000..69b336d67
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/cpuinfo.go
@@ -0,0 +1,117 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import (
+	"bufio"
+	"os"
+	"runtime"
+	"strings"
+
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/log"
+	"github.com/pkg/errors"
+)
+
+// Present the ARM instruction set architecture, eg: v7, v8
+var cpuVariant string
+
+func init() {
+	if isArmArch(runtime.GOARCH) {
+		cpuVariant = getCPUVariant()
+	} else {
+		cpuVariant = ""
+	}
+}
+
+// For Linux, the kernel has already detected the ABI, ISA and Features.
+// So we don't need to access the ARM registers to detect platform information
+// by ourselves. We can just parse these information from /proc/cpuinfo
+func getCPUInfo(pattern string) (info string, err error) {
+	if !isLinuxOS(runtime.GOOS) {
+		return "", errors.Wrapf(errdefs.ErrNotImplemented, "getCPUInfo for OS %s", runtime.GOOS)
+	}
+
+	cpuinfo, err := os.Open("/proc/cpuinfo")
+	if err != nil {
+		return "", err
+	}
+	defer cpuinfo.Close()
+
+	// Start to Parse the Cpuinfo line by line. For SMP SoC, we parse
+	// the first core is enough.
+	scanner := bufio.NewScanner(cpuinfo)
+	for scanner.Scan() {
+		newline := scanner.Text()
+		list := strings.Split(newline, ":")
+
+		if len(list) > 1 && strings.EqualFold(strings.TrimSpace(list[0]), pattern) {
+			return strings.TrimSpace(list[1]), nil
+		}
+	}
+
+	// Check whether the scanner encountered errors
+	err = scanner.Err()
+	if err != nil {
+		return "", err
+	}
+
+	return "", errors.Wrapf(errdefs.ErrNotFound, "getCPUInfo for pattern: %s", pattern)
+}
+
+func getCPUVariant() string {
+	if runtime.GOOS == "windows" {
+		// Windows only supports v7 for ARM32 and v8 for ARM64 and so we can use
+		// runtime.GOARCH to determine the variants
+		var variant string
+		switch runtime.GOARCH {
+		case "arm64":
+			variant = "v8"
+		case "arm":
+			variant = "v7"
+		default:
+			variant = "unknown"
+		}
+
+		return variant
+	}
+
+	variant, err := getCPUInfo("Cpu architecture")
+	if err != nil {
+		log.L.WithError(err).Error("failure getting variant")
+		return ""
+	}
+
+	switch variant {
+	case "8", "AArch64":
+		variant = "v8"
+	case "7", "7M", "?(12)", "?(13)", "?(14)", "?(15)", "?(16)", "?(17)":
+		variant = "v7"
+	case "6", "6TEJ":
+		variant = "v6"
+	case "5", "5T", "5TE", "5TEJ":
+		variant = "v5"
+	case "4", "4T":
+		variant = "v4"
+	case "3":
+		variant = "v3"
+	default:
+		variant = "unknown"
+	}
+
+	return variant
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/database.go b/vendor/github.com/containerd/containerd/platforms/database.go
new file mode 100644
index 000000000..6ede94061
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/database.go
@@ -0,0 +1,114 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import (
+	"runtime"
+	"strings"
+)
+
+// isLinuxOS returns true if the operating system is Linux.
+//
+// The OS value should be normalized before calling this function.
+func isLinuxOS(os string) bool {
+	return os == "linux"
+}
+
+// These function are generated from https://golang.org/src/go/build/syslist.go.
+//
+// We use switch statements because they are slightly faster than map lookups
+// and use a little less memory.
+
+// isKnownOS returns true if we know about the operating system.
+//
+// The OS value should be normalized before calling this function.
+func isKnownOS(os string) bool {
+	switch os {
+	case "aix", "android", "darwin", "dragonfly", "freebsd", "hurd", "illumos", "js", "linux", "nacl", "netbsd", "openbsd", "plan9", "solaris", "windows", "zos":
+		return true
+	}
+	return false
+}
+
+// isArmArch returns true if the architecture is ARM.
+//
+// The arch value should be normalized before being passed to this function.
+func isArmArch(arch string) bool {
+	switch arch {
+	case "arm", "arm64":
+		return true
+	}
+	return false
+}
+
+// isKnownArch returns true if we know about the architecture.
+//
+// The arch value should be normalized before being passed to this function.
+func isKnownArch(arch string) bool {
+	switch arch {
+	case "386", "amd64", "amd64p32", "arm", "armbe", "arm64", "arm64be", "ppc64", "ppc64le", "mips", "mipsle", "mips64", "mips64le", "mips64p32", "mips64p32le", "ppc", "riscv", "riscv64", "s390", "s390x", "sparc", "sparc64", "wasm":
+		return true
+	}
+	return false
+}
+
+func normalizeOS(os string) string {
+	if os == "" {
+		return runtime.GOOS
+	}
+	os = strings.ToLower(os)
+
+	switch os {
+	case "macos":
+		os = "darwin"
+	}
+	return os
+}
+
+// normalizeArch normalizes the architecture.
+func normalizeArch(arch, variant string) (string, string) {
+	arch, variant = strings.ToLower(arch), strings.ToLower(variant)
+	switch arch {
+	case "i386":
+		arch = "386"
+		variant = ""
+	case "x86_64", "x86-64":
+		arch = "amd64"
+		variant = ""
+	case "aarch64", "arm64":
+		arch = "arm64"
+		switch variant {
+		case "8", "v8":
+			variant = ""
+		}
+	case "armhf":
+		arch = "arm"
+		variant = "v7"
+	case "armel":
+		arch = "arm"
+		variant = "v6"
+	case "arm":
+		switch variant {
+		case "", "7":
+			variant = "v7"
+		case "5", "6", "8":
+			variant = "v" + variant
+		}
+	}
+
+	return arch, variant
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/defaults.go b/vendor/github.com/containerd/containerd/platforms/defaults.go
new file mode 100644
index 000000000..a14d80e58
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/defaults.go
@@ -0,0 +1,38 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import (
+	"runtime"
+
+	specs "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// DefaultString returns the default string specifier for the platform.
+func DefaultString() string {
+	return Format(DefaultSpec())
+}
+
+// DefaultSpec returns the current platform's default platform specification.
+func DefaultSpec() specs.Platform {
+	return specs.Platform{
+		OS:           runtime.GOOS,
+		Architecture: runtime.GOARCH,
+		// The Variant field will be empty if arch != ARM.
+		Variant: cpuVariant,
+	}
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/defaults_unix.go b/vendor/github.com/containerd/containerd/platforms/defaults_unix.go
new file mode 100644
index 000000000..e8a7d5ffa
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/defaults_unix.go
@@ -0,0 +1,24 @@
+// +build !windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+// Default returns the default matcher for the platform.
+func Default() MatchComparer {
+	return Only(DefaultSpec())
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/defaults_windows.go b/vendor/github.com/containerd/containerd/platforms/defaults_windows.go
new file mode 100644
index 000000000..0defbd36c
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/defaults_windows.go
@@ -0,0 +1,31 @@
+// +build windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import (
+	specs "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// Default returns the default matcher for the platform.
+func Default() MatchComparer {
+	return Ordered(DefaultSpec(), specs.Platform{
+		OS:           "linux",
+		Architecture: "amd64",
+	})
+}
diff --git a/vendor/github.com/containerd/containerd/platforms/platforms.go b/vendor/github.com/containerd/containerd/platforms/platforms.go
new file mode 100644
index 000000000..d2b73ac3d
--- /dev/null
+++ b/vendor/github.com/containerd/containerd/platforms/platforms.go
@@ -0,0 +1,279 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+// Package platforms provides a toolkit for normalizing, matching and
+// specifying container platforms.
+//
+// Centered around OCI platform specifications, we define a string-based
+// specifier syntax that can be used for user input. With a specifier, users
+// only need to specify the parts of the platform that are relevant to their
+// context, providing an operating system or architecture or both.
+//
+// How do I use this package?
+//
+// The vast majority of use cases should simply use the match function with
+// user input. The first step is to parse a specifier into a matcher:
+//
+//   m, err := Parse("linux")
+//   if err != nil { ... }
+//
+// Once you have a matcher, use it to match against the platform declared by a
+// component, typically from an image or runtime. Since extracting an images
+// platform is a little more involved, we'll use an example against the
+// platform default:
+//
+//   if ok := m.Match(Default()); !ok { /* doesn't match */ }
+//
+// This can be composed in loops for resolving runtimes or used as a filter for
+// fetch and select images.
+//
+// More details of the specifier syntax and platform spec follow.
+//
+// Declaring Platform Support
+//
+// Components that have strict platform requirements should use the OCI
+// platform specification to declare their support. Typically, this will be
+// images and runtimes that should make these declaring which platform they
+// support specifically. This looks roughly as follows:
+//
+//   type Platform struct {
+//	   Architecture string
+//	   OS           string
+//	   Variant      string
+//   }
+//
+// Most images and runtimes should at least set Architecture and OS, according
+// to their GOARCH and GOOS values, respectively (follow the OCI image
+// specification when in doubt). ARM should set variant under certain
+// discussions, which are outlined below.
+//
+// Platform Specifiers
+//
+// While the OCI platform specifications provide a tool for components to
+// specify structured information, user input typically doesn't need the full
+// context and much can be inferred. To solve this problem, we introduced
+// "specifiers". A specifier has the format
+// `<os>|<arch>|<os>/<arch>[/<variant>]`.  The user can provide either the
+// operating system or the architecture or both.
+//
+// An example of a common specifier is `linux/amd64`. If the host has a default
+// of runtime that matches this, the user can simply provide the component that
+// matters. For example, if a image provides amd64 and arm64 support, the
+// operating system, `linux` can be inferred, so they only have to provide
+// `arm64` or `amd64`. Similar behavior is implemented for operating systems,
+// where the architecture may be known but a runtime may support images from
+// different operating systems.
+//
+// Normalization
+//
+// Because not all users are familiar with the way the Go runtime represents
+// platforms, several normalizations have been provided to make this package
+// easier to user.
+//
+// The following are performed for architectures:
+//
+//   Value    Normalized
+//   aarch64  arm64
+//   armhf    arm
+//   armel    arm/v6
+//   i386     386
+//   x86_64   amd64
+//   x86-64   amd64
+//
+// We also normalize the operating system `macos` to `darwin`.
+//
+// ARM Support
+//
+// To qualify ARM architecture, the Variant field is used to qualify the arm
+// version. The most common arm version, v7, is represented without the variant
+// unless it is explicitly provided. This is treated as equivalent to armhf. A
+// previous architecture, armel, will be normalized to arm/v6.
+//
+// While these normalizations are provided, their support on arm platforms has
+// not yet been fully implemented and tested.
+package platforms
+
+import (
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"github.com/containerd/containerd/errdefs"
+	specs "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
+)
+
+var (
+	specifierRe = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)
+)
+
+// Matcher matches platforms specifications, provided by an image or runtime.
+type Matcher interface {
+	Match(platform specs.Platform) bool
+}
+
+// NewMatcher returns a simple matcher based on the provided platform
+// specification. The returned matcher only looks for equality based on os,
+// architecture and variant.
+//
+// One may implement their own matcher if this doesn't provide the required
+// functionality.
+//
+// Applications should opt to use `Match` over directly parsing specifiers.
+func NewMatcher(platform specs.Platform) Matcher {
+	return &matcher{
+		Platform: Normalize(platform),
+	}
+}
+
+type matcher struct {
+	specs.Platform
+}
+
+func (m *matcher) Match(platform specs.Platform) bool {
+	normalized := Normalize(platform)
+	return m.OS == normalized.OS &&
+		m.Architecture == normalized.Architecture &&
+		m.Variant == normalized.Variant
+}
+
+func (m *matcher) String() string {
+	return Format(m.Platform)
+}
+
+// Parse parses the platform specifier syntax into a platform declaration.
+//
+// Platform specifiers are in the format `<os>|<arch>|<os>/<arch>[/<variant>]`.
+// The minimum required information for a platform specifier is the operating
+// system or architecture. If there is only a single string (no slashes), the
+// value will be matched against the known set of operating systems, then fall
+// back to the known set of architectures. The missing component will be
+// inferred based on the local environment.
+func Parse(specifier string) (specs.Platform, error) {
+	if strings.Contains(specifier, "*") {
+		// TODO(stevvooe): need to work out exact wildcard handling
+		return specs.Platform{}, errors.Wrapf(errdefs.ErrInvalidArgument, "%q: wildcards not yet supported", specifier)
+	}
+
+	parts := strings.Split(specifier, "/")
+
+	for _, part := range parts {
+		if !specifierRe.MatchString(part) {
+			return specs.Platform{}, errors.Wrapf(errdefs.ErrInvalidArgument, "%q is an invalid component of %q: platform specifier component must match %q", part, specifier, specifierRe.String())
+		}
+	}
+
+	var p specs.Platform
+	switch len(parts) {
+	case 1:
+		// in this case, we will test that the value might be an OS, then look
+		// it up. If it is not known, we'll treat it as an architecture. Since
+		// we have very little information about the platform here, we are
+		// going to be a little more strict if we don't know about the argument
+		// value.
+		p.OS = normalizeOS(parts[0])
+		if isKnownOS(p.OS) {
+			// picks a default architecture
+			p.Architecture = runtime.GOARCH
+			if p.Architecture == "arm" {
+				// TODO(stevvooe): Resolve arm variant, if not v6 (default)
+				return specs.Platform{}, errors.Wrapf(errdefs.ErrNotImplemented, "arm support not fully implemented")
+			}
+
+			return p, nil
+		}
+
+		p.Architecture, p.Variant = normalizeArch(parts[0], "")
+		if p.Architecture == "arm" && p.Variant == "v7" {
+			p.Variant = ""
+		}
+		if isKnownArch(p.Architecture) {
+			p.OS = runtime.GOOS
+			return p, nil
+		}
+
+		return specs.Platform{}, errors.Wrapf(errdefs.ErrInvalidArgument, "%q: unknown operating system or architecture", specifier)
+	case 2:
+		// In this case, we treat as a regular os/arch pair. We don't care
+		// about whether or not we know of the platform.
+		p.OS = normalizeOS(parts[0])
+		p.Architecture, p.Variant = normalizeArch(parts[1], "")
+		if p.Architecture == "arm" && p.Variant == "v7" {
+			p.Variant = ""
+		}
+
+		return p, nil
+	case 3:
+		// we have a fully specified variant, this is rare
+		p.OS = normalizeOS(parts[0])
+		p.Architecture, p.Variant = normalizeArch(parts[1], parts[2])
+		if p.Architecture == "arm64" && p.Variant == "" {
+			p.Variant = "v8"
+		}
+
+		return p, nil
+	}
+
+	return specs.Platform{}, errors.Wrapf(errdefs.ErrInvalidArgument, "%q: cannot parse platform specifier", specifier)
+}
+
+// MustParse is like Parses but panics if the specifier cannot be parsed.
+// Simplifies initialization of global variables.
+func MustParse(specifier string) specs.Platform {
+	p, err := Parse(specifier)
+	if err != nil {
+		panic("platform: Parse(" + strconv.Quote(specifier) + "): " + err.Error())
+	}
+	return p
+}
+
+// Format returns a string specifier from the provided platform specification.
+func Format(platform specs.Platform) string {
+	if platform.OS == "" {
+		return "unknown"
+	}
+
+	return joinNotEmpty(platform.OS, platform.Architecture, platform.Variant)
+}
+
+func joinNotEmpty(s ...string) string {
+	var ss []string
+	for _, s := range s {
+		if s == "" {
+			continue
+		}
+
+		ss = append(ss, s)
+	}
+
+	return strings.Join(ss, "/")
+}
+
+// Normalize validates and translate the platform to the canonical value.
+//
+// For example, if "Aarch64" is encountered, we change it to "arm64" or if
+// "x86_64" is encountered, it becomes "amd64".
+func Normalize(platform specs.Platform) specs.Platform {
+	platform.OS = normalizeOS(platform.OS)
+	platform.Architecture, platform.Variant = normalizeArch(platform.Architecture, platform.Variant)
+
+	// these fields are deprecated, remove them
+	platform.OSFeatures = nil
+	platform.OSVersion = ""
+
+	return platform
+}